U.S. Attorney John Kacavas said Joseph Cespedes, 37, failed to report the activities of a known drug dealer and then used department resources to help him. On Tuesday, Cespedes pleaded guilty in federal court.

Kacavas said the investigation of Cespedes began in 2011 when the Department of Homeland Security learned that the Manchester police officer was associating with a known drug dealer in Lawrence, Massachusetts. Investigators said the dealer paid him to run criminal records checks on certain stolen identities.

"The drug dealer wanted that information to make sure he could continue to use those stolen identities safely, conceal his status as an illegal immigrant and continue with drug-dealing activities," Kacavas said.

According to Kacavas, Cespedes engaged unwitting Manchester Police Department dispatchers and then sold the results to the dealer for $350 and a small amount of cocaine.

"He was getting these records checks on stolen identities performed, and the dispatchers were thinking this was for legitimate law enforcement purposes, especially on the second one, where he claimed to the dispatcher that he was thinking about buying a car from this person that he was having the record check on," Kacavas said.

The five-year veteran abruptly resigned in January 2012. The dealer was arrested in Massachusetts a month later and implicated Cespedes, investigators said. Police said Cespedes later admitted his actions to investigators in Manchester.

"He violated a trust not only with the city of Manchester, the citizens of Manchester, but also the men and women of the Manchester Police Department," said Chief David Mara. "I'm happy today he is a convicted felon, and I look forward to his sentencing hearing."

Sentencing is set for Nov. 4. Cespedes faces a maximum sentence of three years in prison.